The use of digging blades to form a root ball for trees to be excavated is well known as is also the mounting of the blades for an upright guided movement on a split base or ring frame that is adapted to encircle a tree. It is also well known to utilize hydraulic cylinder units for moving the blades. Machines of this general type are exemplified in U.S. Pat. Nos. 1,599,841; 2,769,278; 3,191,982; 3,364,601; 3,618,234; 3,713,234; 3,775,876; 3,936,960 and 4,031,637. These patents also teach the mounting of tree transplanting machines on trucks and like vehicles such that the excavated tree and the machine can be lifted from the ground and then tilted to a convenient position on the vehicle for transport and later placement of the excavated tree in a hole previously prepared by the machine. The transplanting of trees in this manner has been highly successful.
It is now a rather common practice to transplant trees of a relatively large size, i.e. trees having trunk diameters of from six to ten inches. These size trees create problems in maintaining the machine within dimensions for normal highway travel when mounted on a truck and in the construction of the machine for operation in a clearance relation with low tree branches which occur most often in the handling of coniferous type trees.
In the machines of the above referred to patents, the digging blades are moved by hydraulic cylinder assemblies so that the range of movement of a blade is limited to the piston stroke. A cylinder assembly is thus relatively bulky and required an overall vertical height that is equal substantially to twice the length of the piston stroke. This objection was corrected in part by the hydraulic cylinder and blade assembly of U.S. Pat. No. 4,031,637 wherein the blade travels in a two to one ratio relative to the travel of the piston rod. However, in all of the above patents, it will be seen that hydraulic cylinder units are used for operating the digging blades for the reason that an efficient ground penetration of the blades was believed to require not only their separate operation, but also that ground penetration was facilitated by a reciprocating or bouncing action of the blade during the ground inserting operation.